Re: [PATCH v2] sched: Provide USF for the portable equipment.

From: Dietmar Eggemann <dietmar.eggemann@arm.com>
To: Dongdong Yang <contribute.kernel@gmail.com>,
	gregkh@linuxfoundation.org, rjw@rjwysocki.net,
	viresh.kumar@linaro.org, mingo@redhat.com, peterz@infradead.org,
	juri.lelli@redhat.com, vincent.guittot@linaro.org,
	rostedt@goodmis.org, bsegall@google.com, mgorman@suse.de
Cc: linux-kernel@vger.kernel.org, devel@driverdev.osuosl.org,
	linux-pm@vger.kernel.org, yangdongdong@xiaomi.com,
	tanggeliang@xiaomi.com, taojun@xiaomi.com, huangqiwu@xiaomi.com,
	rocking@linux.alibaba.com, fengwei@xiaomi.com,
	zhangguoquan@xiaomi.com, gulinghua@xiaomi.com, duhui@xiaomi.com
Subject: Re: [PATCH v2] sched: Provide USF for the portable equipment.
Date: Fri, 31 Jul 2020 16:25:56 +0200	[thread overview]
Message-ID: <67e5566b-2ec5-0a1d-87e1-88e90a8fa715@arm.com> (raw)
In-Reply-To: <e992fea6ad249694e615640862a28346936f8844.1596196062.git.yangdongdong@xiaomi.com>

On 31/07/2020 14:46, Dongdong Yang wrote:
> From: Dongdong Yang <yangdongdong@xiaomi.com>

[...]

> +	if (unlikely(usf_vdev.enable_debug))
> +		trace_printk
> +		    ("%s: cpu_id=%d non_ux=%d usf_up=%d usf_down=%d util=%lu\n",
> +		     USF_TAG, cpuid, usf_vdev.usf_non_ux,
> +		     usf_vdev.usf_up_l0, usf_vdev.usf_down, *util);

trace_printk in code ?

> +static int usf_lcd_notifier(struct notifier_block *nb,
> +			    unsigned long val, void *data)
> +{
> +	struct fb_event *evdata = data;
> +	unsigned int blank;
> +
> +	if (!evdata)
> +		return 0;
> +
> +	if (val != FB_EVENT_BLANK)
> +		return 0;
> +
> +	if (evdata->data && val == FB_EVENT_BLANK) {
> +		blank = *(int *)(evdata->data);
> +
> +		switch (blank) {
> +		case FB_BLANK_POWERDOWN:
> +			usf_vdev.is_screen_on = 0;
> +			if (usf_vdev.sysctl_sched_usf_non_ux != 0)
> +				static_branch_enable(&adjust_task_pred_set);
> +			else
> +				static_branch_disable(&adjust_task_pred_set);
> +
> +			break;
> +
> +		case FB_BLANK_UNBLANK:
> +			usf_vdev.is_screen_on = 1;
> +			if (usf_vdev.sysctl_sched_usf_up_l0 != 0 ||
> +			    usf_vdev.sysctl_sched_usf_down != 0)
> +				static_branch_enable(&adjust_task_pred_set);
> +			else
> +				static_branch_disable(&adjust_task_pred_set);
> +			break;
> +		default:
> +			break;
> +		}
> +
> +		usf_vdev.is_sched_usf_enabled = 1;
> +		if (usf_vdev.enable_debug)
> +			trace_printk("%s : usf_vdev.is_screen_on:%d\n",
> +				     __func__, usf_vdev.is_screen_on);
> +	}
> +	return NOTIFY_OK;
> +}
> +
> +static struct notifier_block usf_lcd_nb = {
> +	.notifier_call = usf_lcd_notifier,
> +	.priority = INT_MAX,
> +};

Looks like those notifications should enable/disable the schedutil
extension adjust_task_pred_demand(). Who's calling them?

The 3 sched_usf_FOO sys files somehow have an influence here too. How
should this work?

I see a fb_register_client() in intera_monitor_init further below.

[...]

> +usf_attr_rw(sched_usf_up_l0_r);
> +usf_attr_rw(sched_usf_down_r);
> +usf_attr_rw(sched_usf_non_ux_r);

What can I do with these three files? What do they stand for?

root@h620:/sys/devices/system/cpu/sched_usf# ls
sched_usf_down_r  sched_usf_non_ux_r  sched_usf_up_l0_r

[...]

> +static int __init intera_monitor_init(void)
> +{
> +	int res = -1;
> +	struct attribute_group *attr_group;
> +
> +	res = fb_register_client(&usf_lcd_nb);
> +	if (res < 0) {
> +		pr_err("Failed to register usf_lcd_nb!\n");
> +		return res;

[...]